Liposomes are spherical, self-enclosed vesicles composed of amphipathic lipids. They have been widely studied and have been used as vehicles for in vivo administration of agents, compositions, and compounds. A liposome comprises at least one closed lipid bilayer membrane which defines an aqueous compartment. Liposomes have long been used for drug delivery by encapsulating water soluble agents within the internal aqueous compartment and/or water insoluble agents within the lipid bilayer. Liposomes may be unilamellar, having one lipid bilayer membrane, or multilamellar, having two or more concentrically arranged bilayers.
Various methods of preparing liposomes and encapsulation of therapeutic agents therein are well documented (see, for example, U.S. Pat. Nos. 3,932,657, 4,311,712, and 5,013,556, all of which are incorporated herein by reference). Known methods include the reverse phase evaporation method as described in U.S. Pat. No. 4,235,871, which is incorporated herein by reference.
Many of the known processes for preparing pharmaceutical liposomes are less desirable for nutraceutical liposomes, which are typically intended for oral delivery, due in part to the use of non-food grade ingredients in pharmaceutical liposomal compositions. Further, many of the known processes use a heating step, e.g. heat to solubilize the lipids, which elevates the temperature of the lipid solution. Such processes may affect the performance or efficacy of the agent, compound, or composition, especially those that are sensitive to heat and/or oxidation. Accordingly, additional processes for preparing liposomes, for nutraceutical and pharmaceutical use, are needed.